1. Field of the Invention
The present invention relates to a signal coupling apparatus using a medium voltage power line as a communication line, and more particularly to a signal coupling apparatus which achieves a wide-band high speed communication and is easily installed on and connected between a medium voltage power line and a communications device.
2. Description of the Related Art
Generally, a low-frequency narrow-band signal coupling apparatus using a film capacitor is used as a signal coupling apparatus for communication over a power line. A frequency band usually assigned in a power line communication is less than 450 kHz. Frequency transfer characteristic of the film capacitor satisfies this trend. The conventional power line carrier system has a low speed communication mode with a frequency band of less than 450 kHz. This system usually uses an ultra high-voltage transmission line of more than 66 kV as a transmission line. A coupling capacitor used for the conventional power line carrier system is manufactured as a ground-deferred type with a big size and designed to have a high withstand voltage characteristic, thereby lowering the frequency band. Therefore, this coupling capacitor is not proper in wide band (high speed) communication.
The present invention has been made in view of the above problems, and it is an object of the present invention to provide a signal coupling apparatus for communication over a medium voltage power line, which achieves wide-band high-speed communication, is easily installed on and connected to a medium voltage power distribution line, and is miniaturized.
In accordance with the present invention, the above and other objects can be accomplished by the provision of a signal coupling apparatus for communication by a medium voltage power line, comprising: a housing with an inner cavity; an electrode formed on one end of the housing, one end of the electrode being connected to an external medium voltage lead line; a coupling capacitor disposed within the housing and connected to the other end of the electrode; a drain coil disposed within the housing and connected in series between the coupling capacitor and a power-sided ground terminal connected at a second end of the housing, the coupling capacitor and drain coil forming a high frequency band pass filter; and a communication-sided connection terminal formed on the second end of the housing, one end of the connection terminal being connected to the coupling capacitor and the other end of the connection terminal connected to external communication equipment.
The signal coupling apparatus for communication over the medium voltage power line of the present invention comprises a high withstand voltage capacitor, thereby achieving wide-band high-speed communication of tens of MHz.